A new report published by the Organisation for Economic Co-Operation and Development paints a grim picture of the world in 2050 based on current global trends. It predicts a world population of 9.2 billion people, generating a global GDP four times the size of today's, requiring 80 percent more energy. And with a worldwide energy mix still 85 percent reliant on fossil fuels by that time, it will be coal, oil, and gas that make up most of the difference, the OECD predicts.

Should that prove the case, and without new policy, the report warns the result will be the "locking in" of global warming, with a rise of as much as 6° C (about 10.8° F) predicted by the end of the century. Combined with other knock-on effects of population growth on biodiversity, water and health; the report asserts that the ensuing environmental degradation will result in consequences "that could endanger two centuries of rising living standards."

Ars looked in detail at the 320-page report in order to summarize its key findings.

A brief word on methodology

The OECD report is founded upon both its own ENV-Linkages General Equilibrium model (which derives environmental impacts from economic data, using a database of national economies maintained at Purdue University) and the IMAGE suite of models of the PBL Netherlands Environmental Assessment Agency. Though the report makes projections for greenhouse gas emissions, it relies on prior research to link these to global temperature change.

Peak anthropocene?

According to the report, urban centers will bear the brunt of the population growth, with 70 percent of the world's people living in towns and cities by 2050, compared to just over 50 percent today. Unlike recent trends, it will be towns and cities with less than half a million inhabitants today, rather than the largest super-cities, that will grow most rapidly by 2050. The world's rural population is projected to decrease by 600 million people.

Though economic growth is predicted to be nearly universal, the developed world's proportionate slice of the global economic pie will shrink markedly, with OECD countries' share decreasing from 54 percent in 2010 to under 32 percent by 2050—significantly less than the BRIICS nations' (Brazil, Russia, India, Indonesia, China, and South Africa) share of more than 40 percent. China's GDP is set to overtake that of the United States this year, and India is set to do the same by about 2038, according to the report.

Yet the script departs from the predictable narrative of relentless expansion for China and India. GDP growth rates in these countries will slow as drivers of growth such as education converge with those of the developed world.

It's thought that a quarter of the population of OECD countries will be over 65 by the middle of the century, and the populations of India and China will also age significantly. It's predicted that China's workforce will actually shrink. The populations of Japan and Korea, as well as parts of Europe, will decline; though the trend is not expected to be mirrored in the US and Canada, where immigration is projected to keep the populations growing. Russia's population is predicted to shrink, bucking the trend set by other BRIICS nations.

But the bigger picture is the population growth of non-OECD and non-BRIICS countries (or the Rest of the World, as the report puts it), where the population is expected to grow by an average of 1.3 percent per year. In the period between 2030 and 2050, Sub-Saharan African countries will see the highest economic growth rates in the world, at approximately 6 percent per year. The boom will be spurred in part by rapid growth in Africa's youthful populations, though the continent will remain the least-wealthy in the world. OECD economies, by contrast, are projected to grow by an average of 2 percent per year.

Energy insatiability

And population growth will spur energy consumption. The 80-percent increase predicted by 2050 translates to a total global energy consumption of 900 exajoules (EJ) per year (in other words 9 x 1020 joules)—65 times the annual energy consumption of the US in 2009. This figure factors in continual improvements in energy efficiency, and energy intensity (the ratio of energy consumption to GDP) is set to drop some 40 percent, the report predicts.

Fossil fuels are projected to remain cheaper than renewable sources of energy. The report predicts a 0.5-percent annual growth in oil consumption, and 1.8 percent for coal and natural gas, though oil and gas production are expected to peak by 2050 due to resource depletion. The same is not true of coal, where coal-rich regions happen to coincide with areas of strong economic growth. Use of nuclear energy, biofuels and renewable energy sources are all projected to increase steadily.

The environment in 2050

The report predicts that, as a direct result of increased energy consumption, there will be a 70-percent increase in energy-oriented carbon dioxide emissions, and an overall increase in greenhouse gas emissions of 50 percent. This would correlate to a rise in global average temperature between 3° C and 6° C above preindustrial levels.

Air pollution will overtake contaminated water and lack of sanitation as the prime cause of premature mortality across the globe, potentially rising to 3.6 million deaths per year—mostly in China and India. Death rates caused by ground-level ozone among OECD countries are projected to be among the world's highest, thanks in part to the aging, urbanized populations.

But population growth has more direct effects upon the environment. The world's natural resources are set to undergo unprecedented strain. Water demand is projected to grow by 55 percent by 2050 (including a 400-percent rise in manufacturing water demand), when 40 percent of the global population will live in "water-stressed" areas. The report identifies groundwater depletion as the greatest threat to both agricultural and urban water supplies. Nutrient-pollution of water sources is projected to further deplete aquatic biodiversity. And though the number of people with access to an "improved" water source should increase, the report projects that by 2050, 1.4 billion people will be without basic sanitation. "Improved" does not necessarily equate to "good enough," alas.

With a need to fill more than nine billion bellies, farmland coverage is set to increase worldwide, placing extra pressure on land resources. Though deforestation rates will continue to decline; it's predicted that Earth's mature forests will shrink 13 percent, and global biodiversity will diminish by 10 percent. It isn't all bad news. Thanks in part to slowing global population growth and increasing produce yields, agricultural land coverage is actually predicted to peak before 2030, when deforestation rates should slow further.

Perhaps the least obvious of threats to human health identified in the report is the increasing danger posed by hazardous chemicals, as chemical-production increasingly relocates to developing countries where safety measures are "insufficient."

A closing window of opportunity

The report argues that immediate action not only makes environmental sense, but also economic sense. If global greenhouse emissions can be made to peak before 2020, a 2° C limit to the increase in world average temperature is possible. This would limit the costs of "adaptation and mitigation," but requires "ambitious decisions" to be taken more or less immediately.

The report sets a specific target of stabilizing atmospheric greenhouse gas concentrations at 450ppm. At this level, studies have put the odds of keeping a global temperature rise under 2° C at between 40 and 60 percent. For this level to be achieved, the report calls for putting a "price on carbon" immediately, while implementing a gradual transformation of the energy sector into a low-carbon industry. Finally, the report calls for a wide implementation of "low-cost advanced technologies" that would be stimulated by the higher cost of fossil fuels, giving the example of bio-energy with carbon capture and storage (BECCS)—a technology which the Royal Society has suggested could decrease atmospheric carbon dioxide concentrations by between 50 and 150ppm.

The OECD additionally proposes phasing out fossil fuel subsidies which it claims amounts to $45 billion-75 billion per year in OECD countries, and over $400 billion per year in developing and emerging economies.

Beyond climate change, the report also highlights a number of other actions to mitigate environmental impacts of population growth, with the need to protect natural habitats perhaps foremost among them. Though it acknowledges that 13 percent of the world's land is protected, it claims that grassland, savanna, and marine environments are underrepresented. The report also calls for an end to environmentally harmful subsidies, including those provided to projects or companies which intensify land (or sea) use for agriculture, bioenergy, fishing, forestry, and transport.

The message

The message from the OECD is clear: the status quo is no longer acceptable. "Progress on an incremental, piecemeal, business-as-usual basis in the coming decades will not be enough," it states, quite categorically. And that's not coming from an environmental think tank, but an international body (albeit one with a Eurocentric outlook) with 34 members with the remit of stimulating economic growth and trade.